Paradoxical thoracoabdominal motion refers to the contradictory thoracoabdominal motion in patients with emphysema, i.e., the thoracic motion is outward during inspiration and the abdominal wall motion is inward. So, what are the reasons for the appearance of paradoxical thoracoabdominal motion? Here is a brief introduction. The pathogenesis of obstructive pulmonary emphysema is not fully understood. It is generally believed to be related to bronchial obstruction and protease-antiprotease imbalance. Smoking, infection and atmospheric pollution cause inflammation of the fine bronchial tubes and narrowing or obstruction of the lumen. During inspiration, the lumen of the fine bronchus dilates and air enters the alveoli; during exhalation, the lumen narrows and air is retained, and the intra-alveolar pressure keeps increasing, resulting in over-expansion or even rupture of the alveoli. The loss of radial traction around the fine bronchus causes the fine bronchus to contract, resulting in narrowing of the lumen. Thickening of the intima of the pulmonary vessels, reduction of blood supply to the alveolar wall, and weakening of alveolar elasticity, etc., contribute to the rupture of the inflated alveoli. In the case of infection, the protease activity in the body is increased, and the activity of the anti-protease system is also increased in normal people to protect the lung tissue from destruction. α1 antitrypsin deficient people have a reduced ability to inhibit protease, so they are more likely to develop emphysema. Smoking also has an adverse effect on the protease-antiprotease balance. Patients are advised to actively go to a professional and regular hospital for systematic diagnosis and treatment of this disease, which should never be taken carelessly, as it can lead to chronic pulmonary heart disease and even endanger our lives if we are not careful.